茉莉酮酸酯和水杨酸酯对草食性昆虫细胞色素P450基因表达的诱导

茉莉酮酸酯和水杨酸酯是植物遭受昆虫或病原物攻击时 ,植物产生的激活本身防卫基因的信号物质。这些信号物质的增加 ,可以导致植物他感化合物和防卫蛋白合成增加。旱芹 (ApiumgraveolensCelery)是棉铃虫的寄主植物之一。用茉莉酮酸酯和甲基茉莉酮酸酯诱导旱芹体内花椒毒素和另一种类似的呋喃香豆素化合物香柠檬烯 ,发现处理后2 4h两种毒素开始积累 ,4～ 6d后到达最大值。用人工饲料添加茉莉酮酸酯和水杨酸酯的方法 ,研究棉铃虫 4种P45 0基因 (CYP6B8,CYP6B9,CYP6B2 7andCYP6B2 8)表达。用RT_PCR和XmnI消化及凝胶斑点分析检测处理…     

不同烟粉虱抗性辣椒对外源茉莉酸甲酯的生理响应

以两种不同抗性辣椒品种"苏椒13号"(感烟粉虱)和"新一代三鹰椒"(抗烟粉虱)为对象,研究外源茉莉酸甲酯处理对辣椒叶片叶绿素含量、可溶性糖含量、可溶性蛋白含量、酚类化合物含量以及过氧化物酶和多酚氧化酶活性等的影响。结果表明:不同抗性品种辣椒叶片叶绿素含量、可溶性糖含量、酚类化合物含量以及过氧化物酶和多酚氧化酶的活性均随外源茉莉酸甲酯处理浓度的升高而呈现先升后降的趋势,茉莉酸甲酯响应峰值浓度在10～100μmol·L-1,1000μmol·L-1处理组的各生理指标值均显著低于对照;适宜浓度处理条件下抗虫品种"新一代三鹰椒"的可溶性糖含量、酚类化合物含量显著高于感虫品种"苏椒13号",但可溶性蛋白在处理浓度范围内无显著性变化;受外源茉莉酸甲酯诱导,"苏椒13号"的过氧化物酶及多酚氧化酶的活性均显著高于"新一代三鹰椒",可溶性蛋白含量呈现下降趋势,但在处理浓度范围内无显著性差异;适宜浓度的外源茉莉酸甲酯可诱导辣椒体内的抗虫相关物质向着有利于提高抗烟粉虱的方向改变,不同抗性辣椒品种对外源茉莉酸甲酯的响应程度不同。     

叶片涂施茉莉酸对玉米幼苗防御反应的时间和浓度效应

茉莉酸是环境胁迫下植物产生防御反应的重要信号物质, 但它发挥生理作用的时间和浓度效应以及该效应在叶片和根系中差异性并不清楚。该文以‘高油115’玉米(Zea mays)为材料, 采用4种浓度(1、2.5、5和10 mmol·L^-1)的外源茉莉酸溶液涂施玉米幼苗叶片, 在3~48 h的不同时间内跟踪测定叶片和根系中的直接防御物质(丁布(DIMBOA)和总酚)含量及其合成调控基因(Bx1、Bx9和PAL)、直接防御蛋白调控基因(PR-1、PR-2a和MPI)和间接防御物质挥发物调控基因(FPS和TPS)表达的动态变化。结果表明, 外源茉莉酸处理对玉米叶和根系的化学防御反应具有显著的时间和浓度效应。茉莉酸处理玉米叶片后3~6 h就能诱导叶片中Bx9和PAL基因的表达, 使得丁布和总酚的含量显著增加, 且与处理浓度有呈正比的趋势, 随后诱导作用逐渐减弱; 茉莉酸处理还能明显诱导叶片中PR-2a和MPI基因的表达, 诱导作用分别持续到24和48 h; 在处理后3~6 h内, 高浓度茉莉酸处理对挥发物调控基因FPS表达起诱导作用, 而低浓度茉莉酸则对TPS基因的表达起诱导作用。此外, 茉莉酸处理玉米叶片还能间接影响到根系的防御反应, 但大部分检测指标表明间接诱导作用主要出现在处理后期(24~48 h)。例如, 在处理后48 h, 茉莉酸能系统增加根系中直接防御物质丁布和总酚的含量, 增强根系中防御相关基因PR-2a、MPI、FPS和TPS的表达, 并有随茉莉酸处理浓度的增加而增强的趋势。可见, 外源茉莉酸叶片涂施玉米幼苗对根系的间接诱导作用不如对叶片的直接诱导作用强; 叶片启动防御反应的时间较根系早; 随着处理浓度的增加, 茉莉酸对叶片和根系中防御反应的诱导作用有增强的趋势。     

水稻品种化感特性与农艺性状的关系

选用9个华南地区主栽水稻品种,用特征次生物质标记方法测定它们的化感指数,并通过田间实验确定这些水稻品种的抑草效应及主要农艺性状,在此基础上分析这些水稻品种的化感特性、抑草效应和农艺性状的关系.结果表明,具有化感特性的水稻品种并不都能在田间表现出抑草效应,化感特性与主要农艺性状均无显著的相关性,但同时具有化感特性和有利竞争农艺性状的水稻品种均能在田间显示抑草效应.水稻化感特性和农艺性状的不相关显示化感特性转入相关的水稻品种将不影响它们的农艺性状,这意味着能培育出各种农艺性状的水稻化感新品种.     

外源水杨酸调控水稻化感抑草作用及其分子生理特性

为了探讨外源水杨酸（SA）调控水稻化感抑草效应的可行性,研究了不同浓度的外源SA对强化感水稻PI312777抑草效应的影响及其生理生化特性,并运用实时定量RT-PCR(FQ-PCR)技术检测SA介导的关键酶苯丙氨酸解氨酶基因（ZB8）的相对表达量.结果表明：外源SA能够诱导水稻化感抑草效应增强,而且这种诱导效应与SA的浓度和处理时间相关.叶面喷施SA后,PI312777对稗草的抑制率显著提高,其根系活力、超氧化物歧化酶（SOD）和过氧化物酶（POD）活性增强,过氧化氢酶（CAT）活性降低;而伴生杂草稗草的相应生理指标的变化趋势则相反.PI312777植株中的苯丙氨酸解氨酶（PAL）活性增强,总酚含量升高.0.2 mmol·L^-1的SA诱导水稻化感抑草效应最显著,该浓度下目的基因ZB8的相对表达丰度随处理时间先上调后下调,在24 h达到表达高峰.     

茉莉酸甲酯对丹参毛状根有效成分含量的影响

研究茉莉酸甲酯对丹参毛状根中次生代谢产物含量的影响,为丹参毛状根培养的生产应用提供实验依据。以茉莉酸甲酯作为丹参毛状根的诱导子,进行丹参毛状根诱导培养。发现茉莉酸甲酯诱导的丹参毛状根的丹参酮类化合物丹参酮Ⅰ和丹参酮ⅡA分别是无茉莉酸甲酯诱导的1.53倍和1.16倍,酚酸类化合物迷迭香酸和丹酚酸B分别是无茉莉酸甲酯诱导的1.37倍和4.43倍。茉莉酸甲酯能显著提高丹参毛状根次生代谢产物的合成和积累,通过茉莉酸甲酯诱导实现丹参有效次生代谢产物的高效生产。     

不同诱导因子对落叶松毛虫嗅觉和产卵选择的影响

试验测定了落叶松毛虫幼虫和成虫对茉莉酮、茉莉酸甲酯和水杨酸甲酯3种挥发性信号化合物以及对剪叶损伤、昆虫取食、茉莉酸和水杨酸等诱导因子处理的兴安落叶松的行为反应.结果表明:在0.1%～10% V/V浓度下,茉莉酸甲酯和水杨酸甲酯对幼虫有驱避作用;机械损伤、茉莉酮、茉莉酸、茉莉酸甲酯和水杨酸甲酯均能诱导落叶松产生防御,明显减少了幼虫的取食选择.落叶松毛虫成虫对茉莉酮和水杨酸甲酯有明显的触角电位反应,且雌虫反应敏感性随浓度增加而增强.在诱导因子处理后的落叶松上,成虫产卵量明显减少.     

红汁乳菇醇提物对水稻、稗草的化感影响

研究了红汁乳菇子实体乙醇抽提物对水稻、稗草的化感影响。用不同浓度的红汁乳菇子实体乙醇抽提物处理水稻和稗草种子 ,测量处理后不同时间的水稻和稗草幼苗的根长和苗高 ,按照 Willamson,G.B.的方法计算化感作用效应 (RI)。结果表明 :红汁乳菇乙醇抽提物对稗草幼苗的生长有显著的抑制作用 ,能够导致稗草叶片发黄 ,缩短稗草的根和苗 ,甚至延迟部分种子的萌发。其中 8.5 mg/ ml的乙醇抽提物处理稗草种子后 3d、8d,对根长的化感作用效应分别为 - 0 .98、- 0 .5 8;对苗高的化感作用效应分别为 - 0 .5 0、- 0 .5 1。 6 .5 m g/ ml和 10 .5 mg/ ml处理组的结果与 8.5 mg/ ml处理组的结果在 p=0 .0 5水平上差异不显著。对水稻幼苗的生长表现出一定的调节作用 ,在较低浓度下 (≤ 4 .5 0 mg/ m l)对水稻幼苗有一定促进作用 ,如 4 .5 0 m g/ ml处理水稻种子后 3d、8d,对苗高的化感作用效应分别为 0 .2 5、0 .10 ;在较高浓度下 (如≥ 6 .5 0 mg/ ml)对水稻根长和苗高均为抑制作用 ,6 .5 0 mg/ ml时抑制作用最强 ,处理水稻种子后 3d、8d对幼苗的根长的化感作用效应分别为 - 0 .93、- 0 .4 8;对苗高的化感作用效应分别为 - 0 .5 0、- 0 .2 2 ,在 p=0 .0 5水平上与其它处理组差异显著     

茉莉酸甲酯对菊花抗蚜性的影响

本研究以杭白菊为试验材料,分析茉莉酸甲酯对菊花抗蚜性的影响。供试幼苗叶面喷施不同浓度(0.01、0.05、0.1、0.5、1 mmol·L^-1)茉莉酸甲酯后接种菊姬长管蚜,测定外源茉莉酸甲酯对蚜虫胁迫下菊花叶片的保护酶、防御酶活性、渗透性物质、次生代谢物和茉莉酸途径关键酶基因表达的影响,探究菊花抗蚜性与茉莉酸信号途径的关系。结果表明: 0.01、0.05、0.1、0.5、1 mmol·L^-1浓度的茉莉酸甲酯均显著提高了杭白菊叶片的保护酶、防御酶活性及次生代谢物含量,降低了丙二醛和可溶性糖含量,外源茉莉酸甲酯处理诱导杭白菊CmAOS和CmCOI1的表达,并使内源茉莉酸含量显著增加,杭白菊的抗蚜性增强。     

水稻对受体植物化感作用的遗传生态学研究

选用化感作用潜力差异较大的 5个水稻品种 (系 ) ,按不完全双列杂交设计 (4× 5 )配制成一套包括亲本、F1两个世代的遗传材料 ,在不同环境条件下 ,测定其不同叶龄时期对受体植物莴苣幼苗茎长的抑制作用 .采用包括基因型与环境互作的数量性状加性 显性发育遗传模型 ,分析了水稻化感作用的动态遗传及与环境互作效应 .结果表明 ,水稻叶龄在 7叶期对莴苣茎长的化感作用受加性效应的影响 ,在 3叶期和 6叶期由显性效应控制 ,在 5叶期和 8叶期加性和显性效应均有作用 ,以显性效应为主 ,呈现间断表达的遗传特点 .普通狭义遗传率在 5叶期、7叶期和 8叶期达显著水平 ,随叶龄增大趋于下降 .水稻化感作用受基因型与环境互作效应的影响较大 ,应注意控制水稻生长发育的环境 ,以达到最佳利用水稻化感作用潜力的目的 .     

Allelochemicals released by rice roots and residues in soil

A few rice (Oryza sativa L.) varieties or rice straw produce and release allelochemicals into soil in which interfere with the growth of neighboring or successive plants. Allelopathic rice PI312777 and Huagan-1 at their early growth stages released momilactone B, 3-isopropyl-5-acetoxycyclohexene-2-one-1, and 5,7,4′-trihydroxy-3′,5′-dimethoxyflavone into soil at phytotoxic levels, but non-allelopathic rice Huajingxian did not. Both allelopathic and non-allelopathic rice residues released momilactone B and lignin-related phenolic acids (p-hydroxybenzoic, p-coumaric, ferulic, syringic and vanillic acids) into the soil during residue decomposition to inhibit successive plants. The results indicated that allelochemicals involved in rice allelopathy from living and dead plants are substantially different. Interestingly, the concentrations of the allelochemicals released from the allelopathic rice seedlings in soil increased dramatically when they were surrounded with Echinochloa crus-galli. The concentrations of the allelochemicals were over 3-fold higher in the presence of E. crus-galli than in the absence of E. crus-galli. However, the same case did not occur in non-allelopathic Huajingxian seedlings surrounded with E. crus-galli. In addition to allelochemical exudation being promoted by the presence of E. crus-galli, allelopathic rice seedlings also increased allelochemical exudation in response to exudates of germinated E. crus-galli seeds or lepidimoide, an uronic acid derivative exuded from E. crus-galli seeds. These results imply that allelopathic rice seedlings can sense certain allelochemicals released by E. crus-galli into the soil, and respond by increased production of allelochemicals inhibitory to E. crus-galli. This study suggests that rice residues of both allelopathic and non-allelopathic varieties release similar concentrations and types of allelochemicals to inhibit successive plants. In contrast, living rice plants of certain allelopathic varieties appear to be able to detect the presence of interspecific neighbors and respond by increased allelochemicals.     

Allelopathic Interactions and Allelochemicals: New Possibilities for Sustainable Weed Management

Weeds are known to cause enormous losses due to their interference in agroecosystems. Because of environmental and human health concerns, worldwide efforts are being made to reduce the heavy reliance on synthetic herbicides that are used to control weeds. In this regard the phenomenon of allelopathy, which is expressed through the release of chemicals by a plant, has been suggested to be one of the possible alternatives for achieving sustainable weed management. The use of allelopathy for controlling weeds could be either through directly utilizing natural allelopathic interactions, particularly of crop plants, or by using allelochemicals as natural herbicides. In the former case, a number of crop plants with allelopathic potential can be used as cover, smother, and green manure crops for managing weeds by making desired manipulations in the cultural practices and cropping patterns. These can be suitably rotated or intercropped with main crops to manage the target weeds (including parasitic ones) selectively. Even the crop mulch/residues can also give desirable benefits. Not only the terrestrial weeds, even allelopathy can be suitably manipulated for the management of aquatic weeds. The allelochemicals present in the higher plants as well as in the microbes can be directly used for weed management on the pattern of herbicides. Their bioefficacy can be enhanced by structural changes or the synthesis of chemical analogues based on them. Further, in order to enhance the potential of allelopathic crops, several improvements can be made with the use of biotechnology or genomics and proteomics. In this context either the production of allelochemicals can be enhanced or the transgenics with foreign genes encoding for a particular weed-suppressing allelochemical could be produced. In the former, both conventional breeding and molecular genetical techniques are useful. However, with conventional breeding being slow and difficult, more emphasis is laid on the use of modern techniques such as molecular markers and the selection aided by them. Although the progress in this regard is slow, nevertheless some promising results are coming and more are expected in future. This review attempts to discuss all these aspects of allelopathy for the sustainable management of weeds. Referee: Dr. Amrjits S. Basra, Central Plains Crop Technology, 5912 North Meridian Avenue, Wichita, KS 67204     

Allelopathic substance in rice root exudates: rediscovery of momilactone B as an allelochemical

Much research on rice allelopathy has been directed toward the selection of allelopathic rice strains and the identification of allelochemicals in rice. This paper briefly summarizes recent progress in the rice allelopathy and focuses on rediscovery of momilactone B as an allelochemical. A large number of rice varieties were found to inhibit the growth of several plant species when grown together under field and/or laboratory conditions. These findings suggest that rice probably produces and releases allelochemical(s) into the environment. The putative compound causing the inhibitory effect of rice was recently isolated from rice root exudates, and the chemical structure of the inhibitor was determined by spectral data as momilactone B. In addition, it has been found that momilactone B is released from rice roots into the neighboring environment, and the release level of momilactone B from rice may be sufficient to cause growth inhibition of neighboring plants. These findings suggest that momilactone B may play an important role in rice allelopathy.     

Interference of allelopathic rice with paddy weeds at the root level

• Despite increasing knowledge of the involvement of allelopathy in negative interactions among plants, relatively little is known about its action at the root level. This study aims to enhance understanding of interactions of roots between a crop and associated weeds via allelopathy.
• Based on a series of experiments with window rhizoboxes and root segregation methods, we examined root placement patterns and root interactions between allelopathic rice and major paddy weeds Cyperus difformis, Echinochloa crus‐galli, Eclipta prostrata, Leptochloa chinensis and Oryza sativa (weedy rice).
• Allelopathic rice inhibited growth of paddy weed roots more than shoots regardless of species. Furthermore, allelopathic rice significantly reduced total root length, total root area, maximum root width and maximum root depth of paddy weeds, while the weeds adjusted horizontal and vertical placement of their roots in response to the presence of allelopathic rice. With the exception of O. sativa (weedy rice), root growth of weeds avoided expanding towards allelopathic rice. Compared with root contact, root segregation significantly increased inhibition of E. crus‐galli, E. prostrata and L. chinensis through an increase in rice allelochemicals. In particular, their root exudates induced production of rice allelochemicals. However, similar results were not observed in C. difformis and O. sativa (weedy rice) with either root segregation or root exudate application.
• The results demonstrate that allelopathic rice interferes with paddy weeds by altering root placement patterns and root interactions. This is the first case of a root behavioural strategy in crop–weed allelopathic interaction.

     

Allelopathy in the natural and agricultural ecosystems and isolation of potent allelochemicals from Velvet bean (Mucuna pruriens) and Hairy vetch (Vicia villosa).

We have studied on allelopathy of plants and developed methods to identify the effective substances in root exudates, leaf leacheate, and volatile chemicals emitted from plants. We found traditional cover plants that show allelopathic activity are useful for weed control. It could eliminate the use of synthetic chemicals for this purpose. Allelopathy is a natural power of plants to protect themselves by producing natural organic chemicals. Some endemic plants in Asia, already known by farmers in the region, as either cover crops used in intercropping, hedgerow, or agroforestry, were found to possess strong allelopathic abilities. Our group identified several allelochemicals from these plants. These allelopathic cover crops, mostly leguminous plants, provide protein rich food, and grow easily without artificial fertilizers, herbicides, insecticides and fungicides. In this regards, these allelopathic cover crops could save food shortage in rural area, and are useful for environmental conservation. Screenings of allelopathic plants by specific bioassays and field tests have been conducted. Hairy vetch (Vicia villosa) and Velvet bean (Mucuna pruriens) are two promising species for the practical application of allelopathy. An amino acid, L-DOPA, unusual in plants, plays an important role as allelochemical in Velvet bean (Mucuna pruriens). Hairy vetch is the most promising cover plant for the weed control in orchard, vegetable and rice production and even for landscape amendment in abandoned field in Japan. We have isolated "cyanamide", a well known nitrogen fertilizer, from Hairy vetch. This is the first finding of naturally produced cyanamide in the world.     

Allelopathy in wheat (Triticum aestivum)

Wheat (Triticum aestivum) allelopathy has potential for the management of weeds, pests and diseases. Both wheat residue allelopathy and wheat seedling allelopathy can be exploited for managing weeds, including resistant biotypes. Wheat varieties differ in allelopathic potential against weeds, indicating that selection of allelopathic varieties might be a useful strategy in integrated weed management. Several categories of allelochemicals for wheat allelopathy have been identified, namely, phenolic acids, hydroxamic acids and short‐chain fatty acids. Wheat allelopathic activity is genetically controlled and a multigenic model has been proposed. Research is underway to identify genetic markers associated with wheat allelopathy. Once allelopathic genes have been located, a breeding programme could be initiated to transfer the genes into modern varieties for weed suppression. The negative impacts of wheat autotoxicity on agricultural production systems have also been identified when wheat straws are retained on the soil surface for conservation farming purposes. A management package to avoid such deleterious effects is discussed. Wheat allelopathy requires further study in order to maximise its allelopathic potential for the control of weeds, pests and diseases, and to minimise its detrimental effects on the growth of wheat and other crops.     

The chemical-mediated allelopathic interaction between rice and barnyard grass

Aims

The possible involvement of the chemical-mediated interaction in allelopathy between rice and barnyard grass was investigated.

Methods

Effcts of rice seedlings and rice root exudate on the alleloapthic activity of barnyard grass were determined and a key compound invovled in the allelopathic interaction between rice and barnyard grass was isolated.

Results

Allelopathic activity of barnyard grass was increased by the presence of rice seedlings. Rice root exudates also elevated the allelopahtic activity of barnyard grass. A key compound, which increased the allelopathic activity of barnyard grass, in the rice root exudates was isolated and determined as momilactone B. Momilactone B increased the allelopathic activity of barnyard grass at concentrations greater than 3 μM, and increasing the momilactone B concentration increased the activity.

Conclusions

Momilactone B is known to act as a potent rice allelochemical and to possess strong growth inhibitory activity against barnyard grass. The present research suggests that barnyard grass may response to the presence of neighboring rice by sensing momilactone B in rice root exudates and increase allelopathic activity. Thus, momilactone B may not only act as a rice allelochemical but also play an important role in rice-induced allelopathy of barnyard grass. The induced-allelopathy may provide a competitive advantage for barnyard grass through the growth inhibition of competing plant species including rice. Barnyard grass allelopathy may be one of the inducible defense mechanisms by chemical-mediated plant interaction between rice and barnyard grass. Rice allelopathy was also reported to be increased by the presence of barnyard grass through increasing production and secretion of momilactone B into surrounding environments. During the evolutional process, rice and barnyard grass may have developed the chemical cross talk to activate the defense mechanisms against some biotic stress conditions by detection of certain key compounds.     

The fungal fast lane: common mycorrhizal networks extend bioactive zones of allelochemicals in soils

Allelopathy, a phenomenon where compounds produced by one plant limit the growth of surrounding plants, is a controversially discussed factor in plant-plant interactions with great significance for plant community structure. Common mycorrhizal networks (CMNs) form belowground networks that interconnect multiple plant species; yet these networks are typically ignored in studies of allelopathy. We tested the hypothesis that CMNs facilitate transport of allelochemicals from supplier to target plants, thereby affecting allelopathic interactions. We analyzed accumulation of a model allelopathic substance, the herbicide imazamox, and two allelopathic thiophenes released from Tagetes tenuifolia roots, by diffusion through soil and CMNs. We also conducted bioassays to determine how the accumulated substances affected plant growth. All compounds accumulated to greater levels in target soils with CMNs as opposed to soils without CMNs. This increased accumulation was associated with reduced growth of target plants in soils with CMNs. Our results show that CMNs support transfer of allelochemicals from supplier to target plants and thus lead to allelochemical accumulation at levels that could not be reached by diffusion through soil alone. We conclude that CMNs expand the bioactive zones of allelochemicals in natural environments, with significant implications for interspecies chemical interactions in plant communities.